It seems that just like Gnome 2.4, KDE 3.2 uses something other then the typical XDM style Xsessions file to login to varies Desktop Environments. I found that by editing the KDMRC file to point to Gnomes Xsessions file gave me the fix I needed to get KDM to work correctly...
If you have Gnome 2.4 installed and are using Slackware and can't get KDM to login to any other desktop then it's own, then edit these two lines in yr KDMRC file to get it working correctly.
From this: (BROKEN)
Session=/opt/kde/share/config/kdm/Xsession
SessionsDirs=/opt/kde/share/apps/kdm/sessions
To This: (FIXED)
Session=/etc/X11/gdm/Xsession
SessionsDirs=/etc/X11/dm/Sessions
By telling it to use that "Xsessions" file and the *.desktop files in the "/dm/Sessions" directory, you should be able to have a fully operational KDM again.
Also I am pretty sure there is another fix for this and I know it has something to do with the way Gnome sets up there Xsession file. If you should happen to figure it out, could you please post that info here... Thanx!
Good Luck!